Garden Rx: Get Dirty to Ward off Asthma and Allergies

Alien worlds and weird encounters are the stuff of sci-fi yarns. However, recent findings in the field of microbial ecology, regarding how microorganisms inhabiting our core are inextricably linked to the natural world around us, tell an even stranger story.

Research suggests that the tiniest of critters have been sending subtle signals to trillions of microorganisms that inhabit the human body, which scientists believe play a critical role in human physiology.

Known as the microbiome, every single human cell houses more than 10 species of microbes. These creatures live and die in the uncharted habitats of the human body, where scientists are just beginning to explore their potential impact on regulating the immune system and boosting overall health.

Many of these microbes dwell inside the coiled linings of our large intestine and are believed to aide the autoimmune system, which we rely upon to fend off debilitating diseases. It has become increasingly apparent to environmentalists that severing the connection between our domesticated microbes and the natural world might put our health at risk.

The thinking goes like this: People need to venture outside the sanitary conditions of our indoor habitats and engage with nature more often. Getting grubby is good for you. Even spending time working in a backyard or community garden would reap huge benefits, given that gardens are places where we are likely to encounter legions of microbes that have co-evolved with us over millennia.

Author Michael Pollan advanced this thesis regarding our symbiotic relationship with beneficial microbes in a recent The New York Times Magazine article, "The Secret Lives of Our Germs," expanding on an idea dubbed the hygiene hypothesis posited by Dr. David Strachman 25 years ago.

Strachman introduced the idea that the high rate of autoimmune disorders among the cosseted inhabitants of the industrialized world could be due to the relative absence of microbes, linking the lack of grime in clean, hyper-efficient cities to surging rates of allergies and asthma in the latter half of the 20th century.

What followed has been an ongoing debate on the role that microbial diversity has on human health. Advocates contend that ending the primal ties our bodies had with nature has had unintended consequences. As evidence, they cite research studies of rural farm populations and remote tribes that have repeatedly shown a marked absence of autoimmune disorders prevalent in modern society.

Exposed to a fine layer of filth, pollen and microbes not present in Western cities, these disparate populations remain remarkably healthy, leaving scientists to ponder what accounts for their resilience, despite the abundance of germs and bacteria present in the food, air and water. Along with robust immune systems, researchers discovered a much greater diversity of microbes residing in the guts of Amerindians and rural Africans living in the rainforest. All of this evidence reveals that populations living in close contact with their natural environment, and often to each other, tend not to suffer from chronic autoimmune disorders.

These studies suggest that if you want to stay healthy, pay attention to dirt. A thimbleful of soil contains a menagerie of protozoa, algae, nematodes, bacteria and fungi carrying out their various metabolic functions. For as long as humans have walked upright, we've been in constant contact with these microscopic heroes. We ingest them in our food, bathe with and inhale them. Some of these microbes took up residence in our intestines eons ago, while other introduced species appear to have taken on critical tasks serving as sentries and traffic cops. In the past, city dwellers could expect a steady influx of these microbial allies to provide important ecosystem services. Without their key inputs, the immune system can go haywire.

While modern sanitation has saved countless lives, exposure to healthy soil is beneficial for maintaining a healthy immune system. The presence of microorganisms provides the immune response with information it needs to function properly, heeding dangerous threats and ignoring others, while encouraging gut flora to go about their unbidden business. So the next time you're pulling weeds, turning compost or performing some other tedious task in the garden, remember the myriad of unseen allies that share the space.